3a 



Exj->eriment No. 2. 



DETERMINATION OF HYGROSCOPIC MOISTCRE. 



Use the air-dried soils from experiment No. 1. 



1. Place al)out 10 grams of the air-dried soil in a tared porcelain crucible {a) . 



2. Weigh the soil and crucible [h] and heat in the air bath at 100 to 110° C. for 

 1 hour. 



3. Cool in a desiccator and weigh rapidly to prevent absorption of moisture from 

 the air. 



4. Heat for a shorter time, cool, and weigh, repeating until the weight (c) becomes 

 constant. 



Calculation: The loss of weight, or h — r, equals the amount of hygroscopic water 



in the sample taken. 



c—a equals the weight of water-free soil. 



/>— (• 

 Therefore ^— ^ = per cent of hygroscopic water expressed on the basis of water-free 



soil. 



The per cent of hygroscopic water found was: Sand, 

 -; gravel, 



-; clay, 



loam, 



Define hygroscopic water: 



From the results obtained in experiments 1 and 2 compute the percentage of cap- 

 illary and total water in the soil, expressed on the basis of water-free soil. 



Total water content is (percentage) . Sand, ; clay, ; loam, ; 



gravel, . 



In addition to the capillary and hygroscopic water, the soil may contain, under 

 some conditions, as immediately after a rain, a certain amount of free or gravita- 

 tional water. This portion of the soil water is acted upon by the force of gravity, 

 which causes it to percolate downward to the level of the ground water. 



Experiment No. 3. 

 hilgard's flocculation experiment. 



Two students will work conjointly in this experiment. 



1. Into each of four beakers place about 1 gram of clay and add 200 cubic centi- 

 meters of water. 



2. To beaker- 



No. 1 add 0.2 gram calcium hydrate=0.1 per cent solution. 

 No. 2 add 1 gram calcium hydrate=0.5 per cent solution. 

 No. 3 add 2 grams calcium hydrate=l per cent solution. 

 No. 4 add gram calcium hydrate = Control. 



3. With a stirring rod mix the contents of each ])eaker thoroughly and then place 

 a sam])le of eacli in a Nessler's cylinder and whirl in the centrifuge at the lowest 

 speed and note the time required to completely precipitate each solution. 



4. Pour the contents of each cylinder back into the respective beaker, stir thor- 

 oughly and set aside, observing occasionally to determine the time required for com- 

 plete sedimentation in each case. 



Compare in each case the cylinders and beakers containing the different strengths 

 of solution and the control and tabulate the results in the space below. 



Time to cen- 

 trifugate. 



0.1 per cent .solution 

 0.5 per cent solution 

 1 per cent solution . . 

 Control 



Time to 

 sediment. 



Explain how the lime acts and clarifies the water: 

 26777— No. 127—03 3 



